1. Field of the Invention
This invention is in the field of composite articles formed by bonding together piles of a consolidated monotape which have been pre-shaped to the extent that the bonding process does not cause significant distortion due to movement of the filaments within the monotape.
2. Description of the Prior Art
There has been increasing emphasis in recent times on the use of metal matrix composite articles for high temperature service, such as for use in turbine engine blades. Metal matrix composite blades are complex assemblies which may be made up of any one of a number of high strength-high modulus reinforcing filaments, a suitable matrix material in various forms, together with dovetail root blocks, root splaying wedges or shims and leading edge inserts. In the manufacture of such blades, the aerodynamic shape or volume of the blade must be precisely filled with these pieces without mislocation of or breaks in the reinforcing filaments, and without voids, cracks or inclusions in the matrix material.
As an example of the prior are in this area, there is the Gray U.S. Pat. No. 3,600,103 which issued on Aug. 17, 1971. This patent describes a compressor or fan blade made up of layers of high modulus fibers extending in parallel relation, the fibers being secured to an aluminum alloy sheet by means of a coating of an aluminum alloy. Sheet plies of this material are then stacked together in essentially flat relationship and bonded under high temperature and pressure to compact the plies and to cause the aluminum alloy to flow to fill the voids.
Kreider U.S. Pat. No. 3,699,623 which issued on Oct. 24, 1972 describes a method for protecting fiber reinforced aluminum matrix composite components which involves sheathing the composite with a protective skin of titanium or titanium alloy.
Stone U.S. Pat. No. 3,731,360 which issued on May 8, 1973 deals with a method of bonding a composite blade with an integrally attached root, wherein the composite fibers are compacted and the root blocks are bonded to one end of the layers of fibers in a single pressing and bonding operation.
In fabrication procedures where the blade preform is constructed flat or on a contour block using essentially flat plies, there will be lateral and axial flow of material as it is redistributed to fill the volume. Results achieved by such an approach are unpredictable and not necessarily reproducible. With the pieces involved having to move about to conform to the fixed volume of the tool, hard and soft spots can result which can cause undesirable filament breaks and/or voids.